The non-binding resolution drafted by Qatar welcomes the main opposition coalition as an "effective" dialogue participant needed for a political transition in Syria. It notes the group's widespread international acceptance as the legitimate representative of the Syrian people.

The resolution also demands that Syria give a U.N. team free access to investigate alleged uses of chemical weapons. That team authorized by U.N. Secretary-General Ban Ki-moon is ready to deploy, but Syria has not allowed them into the country.

Russia opposes the resolution, and diplomats say the document is expected to earn less support than a previous resolution the General Assembly passed last August.

Twelve countries, including Russia, China and Iran, voted against the earlier resolution, which Syria rejected as a "piece of theater" that would have no effect.

The new document reiterates condemnation for Syrian forces using heavy weapons in populated areas, and also urges all sides to allow humanitarian workers to move freely inside of Syria.

The vote comes as efforts continue to try to arrange a Syrian peace conference.

U.S. Secretary of State John Kerry said Tuesday he expects the Syrian government and the main opposition to attend a conference in early June.

Amid reports the Syrian government needs more details before deciding whether to attend, Kerry said boycotting the meeting would be a "miscalculation" and drum up more support for the opposition.

He said last week that the outcome of a peace conference could influence a U.S. decision whether to arm the opposition.

Russia and the United States agreed last week to arrange peace talks despite their sharp disagreements over Syria. Russia is a long-time ally of Assad, while the United States has been sending non-lethal aid to the rebels.

Ban is due to meet with Russian officials later this week to discuss the situation in Syria.